Photoelectric conversion elements include a variety of types depending on the structure and application thereof, such as a LED (Light Emitting Diode), a LD (Laser Diode), a PD (Photo Diode) and a solar cell. The development of photovoltaic power generation for generating electric power using a solar cell is actively promoted as renewable energy is increasingly required.
The solar cell is essentially structured so as to efficiently generate electric power by receiving sunlight. On the other hand, portable information device have come into wide use as small and multi-functional information devices as represented by smart phones.
For example, the required amount of electric power increases as the portable information device becomes multi/high-functionalized. However, the capacity of a built-in battery, such as a lithium battery, which stores electric power is limited. Therefore, such a problem arises that the frequency of charging the portable information device is increased.
Thus, if electric power can be generated by a high-efficiency solar cell to cover power consumption, the charge frequency can be reduced, so that a portable information device of high practicality can be achieved. Particularly, if a photoelectric conversion element that allows power generation of high efficiency with indoor illumination light having a light intensity lower than that of sunlight is achieved, the usefulness of the portable information device is enhanced.